The invention relates to a method for rolling plates by at least one rolling stand.
In order to allow the edges of a rectangular plate to be aligned when it is guided into a rolling stand of a sheet rolling mill, lateral guiding elements are provided which ensure the linear and symmetrical course of the plate. The guiding elements have a centering function and effectively act as a “barrier” thereafter. Said guiding elements do not abut the side faces of the plate in this case, but are positioned at a distance from the side faces such that gaps having a width of several centimeters, in particular 3 to 5 cm, are formed between the guiding elements and the side faces of the plates. When rolling rectangular plates or sheets, it often occurs that the edges of the plates are not aligned when they enter the roll gap of the rolling stand of the sheet rolling mill. This situation can arise if the friction differs in the various regions of the rolled plate, for example. As a result of this, the plate is no longer right-angled after the rolling pass, but assumes the shape of a parallelogram. This effect is further amplified in the next rolling pass, since the plate is initially grasped on only one side of the roll gap and therefore transverse forces occur. As a result of the transverse forces, the plate is however rotated relative to the rolling direction, to the extent that this allowed by the guiding elements. Within these limits, the plate therefore runs obliquely into and through the roll gap.
The above-described phenomenon results in significant instabilities and problems which can adversely affect the production, particularly when rolling thin and wide plates. Various existing methods endeavor to ensure that plates which have lost their squareness are as aligned as possible when guided into the roll gap. According to one possibility, plates whose width is greater than their length in a rolling direction are thrust into the roll gap at excessive speed and thereby aligned. A further possibility is to move the guiding elements as close together as possible, though this is limited because the plates are generally wider at the leading and trailing ends, and become jammed in the side guide.